Prepare Bowl and Cereal: Grease a large mixing bowl with butter, or spray it with cooking spray. Pour the Rice Krispies Cereal into the bowl and set aside.

Melt Butter: Begin to melt the butter in a medium-large saucepan set over low heat.

Add Marshmallows: Add the marshmallows to the melted butter and stir to coat.

Melt Marshmallows: Continue to heat the marshmallows, stirring occasionally, until about ¾ of them are melted. Then remove the pan from the heat, and continue to stir, smashing the marshmallows, until they have all melted.

Add Extract and Coloring: Stir in the peppermint extract and green food coloring (about 10 drops if using liquid coloring). Stir until the color is evenly distributed.

Coat Cereal: Pour the melted marshmallow mixture over the cereal in the large bowl. Toss to coat the cereal evenly.

Cool Slightly: Let the mixture cool for 5-8 minutes, until it feels cool to the touch. This prevents the chocolate chips from melting completely when they’re added.

Add Chocolate Chips: Reserve about 3 tablespoons of the mini chocolate chips for topping, then toss the rest into the cereal mixture. Stir until combined.

Press into Pan: Spread the mixture into a well-buttered 8-inch square pan.

Add Topping: Sprinkle the reserved mini chocolate chips over the top and press them into the cereal treats using the back of a rubber spatula or spoon.

Cool and Set: Allow the treats to cool completely at room temperature for at least 30 minutes.

Cut and Serve: Remove the treats from the pan and cut into 16 squares